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> One of the wonderful things about 64 bit address spaces? You don't ever have to re-use an address. Never say never. Current x86-64 CPUs only support 48 bits
by haberman 14y ago
> One of the wonderful things about 64 bit address spaces? You don't ever have to re-use an address.
Never say never. Current x86-64 CPUs only support 48 bits of address space, which you could scan through in under two hours on a 2.5GHz machine (at 16 bytes/cycle). 48 bits is a lot, but not infinite.
If and when it actually is 64 bits, that will be a different story. :)
- crpatino 14y agoAmen to that! I remember how wonderful it was to have this flat 32-bit address space, where each memory location could be unambiguously identified by a single numeric address, and you did not have to make any crazy distinctions between short and long pointers.
- ChuckMcM 14y agoTrue, the physically addressable memory is "only" 256TB but the virtual space is still 64 bits. The point in time when the 256TB becomes a problem is when your working set (stuff resident in memory) is ideally more than 256TB. We've got mostly 96GB machines and those are modestly hard to exhaust. I don't think even a 1TB physical memory machine would be exhaustible with our current data sets. Even today, reading in a 32GB index shard from SSD still takes a couple of minutes.